I have been asked to apply a really thick layer of conformal coating to my printed circuit board. What are the problems with this approach?

Applying conformal coating really thick is not a good idea especially if you exceed the recommended thickness from the manufacture.

There are several reasons for this but the two key ones are:

  1. Applying a thick coating can cause long-term reliability issues. This is because the conformal coating can crack and craze in the long-term. It can also possibly cause damage to the PCB due to Coefficient of Thermal Expansion (CTE) mismatch between components and the coating.
  2. Defects like bubbles can occur when applying really thick conformal coating layers.

If in doubt, more is not better. Conformal coatings are not designed as encapsulates and potting compounds. The IPC and mil spec recommend certain thicknesses such as 30-150um for acrylics. It’s a good idea to keep within these tolerances and use conformal coating thickness measurement systems to check.

For further information on Coating Thickness application issues or other areas please contact us here at +44 1226 249019 or email sales@schservices.com


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About Dr Lee Hitchens

Dr Hitchens has been working in the electronics industry and the area of conformal coatings for over 25 years in various areas including sales and technical support. He has also been training people for almost the same amount of time in all areas of conformal coating whether that is materials & equipment selection, process development or troubleshooting to help them solve their particular problem. Recently, he decided that the industry needed a specific place where all of the useful knowledge on conformal coatings could be collated for users to find easily and use in their own production process. So, Nexus was born and he began the Nexus eBook project.

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